Motion blur is the visible blur that appears on an image or video sequence of a film or animation when it comprises an object in movement. This blur is due to a rapid displacement of the object during the capture of the image or to a long exposition duration (pose time) of the image capture device (camcorder or fixed camera). The captured image integrates all of the positions of the object over a period corresponding to the exposition duration determined by the shutter speed of the image capture device. In this image, an element of the captured scene that is in movement with respect to the capture device then appears blurred in the direction of the movement. This blurred element can be an object in movement of the scene when the image capture device is fixed, or the background of the scene when the image capture device moves at the same speed as the objects in movement of the scene.
In the case of synthesis images, each image can be assimilated with an image that will be captured by a capture device having an infinite shutter speed (exposition duration quasi-null). There is thus no motion blur and the displacement of objects in movement in the images appears discontinuous and juddered to the human eye.
As concerns the images generated by a capture device with a digital shutter (non-mechanical, the representation of the object in movement on the captured image can contain temporal artefacts that are disagreeable to the human eye due to the abrupt truncation of the light signal by the digital shutter that typically operates in start/stop mode, that is to say with only 2 possible states for the shutter.
To overcome this problem, it is known to those skilled in the art to apply to these images a processing simulating the filtering incurred by a mechanical shutter. For the images generated by a capture device with a digital shutter, this processing consists in according the temporal response of the digital shutter with that of a mechanical shutter. For synthesis images, the processing consists in filtering the image with a filter called a “motion filter”, having a temporal response close to that of a mechanical shutter.
This processing generally consists in acquiring a plurality of video images over an interval of time centred on a reference time t relating to the image to be displayed, in weighting each of said video images and in implementing a display of the image associated with the reference time t by averaging weighted video images. The number of images to be weighted and the value of weighting factors to be considered for this processing depends on the temporal response to be reproduced.
This processing requires obtaining and saving, for each image to be displayed, several video images. Its implementation thus requires a large memory space to store these images and implicates relatively long memory access time, which has an influence on the processing time.